1. Field of the Invention
The present invention relates to cranes, and more particularly relates to a mobile truck crane having a boom and other components connected to its chassis for pivotal movement only about a horizontal axis relative to the chassis; said chassis having its end portions rotatably supported on a ground supported ring with the entire chassis raised above the ground and selectively pivoted about a vertical axis concentric with the ring during operation.
2. Description of the Prior Art
Self-propelled truck cranes having a chassis mounted on wheels or crawler tracks with an upper works and boom supported on the chassis for pivotal movement about a vertical axis relative to the chassis are well known in the art. U.S. Pat. No. 4,053,058 to Jensen et al which issued on Oct. 11, 1977; and U.S. Pat. No. 4,016,688 to Tiffin et al which issued on Apr. 12, 1977 disclose cranes which have upper works pivoted about vertical axes.
German Pat. No. 2,554,910 which was published on June 6, 1977 discloses a truck crane with the upper works eliminated so that the chassis or lower works supports the drive motor, hydraulic motors and other standard crane components including the lower end of the jib or live mast which is pivoted to the chassis for vertical movement about a horizontal axis by a hydraulic cylinder. A multisection ground supported ring is placed at the working site with one section being removed so that the crane can be driven within and centered relative to the ring. The removed section is replaced to define a completed ring; and hydraulic jacks are then operated to lift the crane chassis and wheels off the ground. A front end piece and a rear end piece, with ring engaging rollers journaled thereon, are then secured to the chassis ends for supporting the boom for horizontal pivotal movement and for supporting a counterweight, respectively. The jacks are then lowered so that the entire crane is supported by the ring and is selectively rotated about a vertical axis by front and rear hydraulically driven pinions which mesh with a ring gear secured to the ring. Thus, this patented structure necessitates the connection of two end pieces to the chassis after the chassis has first been centered relative to the ring and raised above the ring, and then requires that the ring engaging rollers be lowered onto the ring before the crane can be placed in operation.
U.S. Pat. No. 3,528,675 which issued to Brown on Sept. 15, 1970; and U.S. Pat. No 3,777,898 to Gallay which issued on Dec. 11, 1973 each disclose a mobile crane which carries a turntable and outriggers with cooperating jacks which lift the wheels of the vehicle off the ground permitting the chassis and supported components to be rotated about a vertical axis by a powered pinion and ring gear assembly.
U.S. Wittman et al application Ser. No. 138,461 which was filed on Apr. 4, 1980 and is assigned to the assignee of the present invention, is somewhat pertinent in that the boom, its load, and the counterweight are supported by a ground supported ring. However, the crane differs from the crane of the present invention since it includes an upper works rotatable about a lower works, and since the tracks (or wheels) which support the lower works remain on the ground at all times.
Assignee's Dvorsky et al U.S. Pat. No. 4,196,816 which issued on Apr. 8, 1980 includes a ring that is supported on jacks which support the load and counterweight during operation. However, this patent differs from that of the present invention since it includes a lower works which pivotally supports and drives an upper works about a vertical axis, and the track (or wheels) are not rotated relative to the ring but are anchored thereto during operation.